1. Field of the Invention
The present invention relates to a method of driving an image display apparatus, and more particularly to a method of driving an image display apparatus especially suitable for an active matrix liquid display apparatus for example.
2. Description of the Prior Art
Examples of known configurations of pixels in a color image display apparatus which uses a liquid crystal are shown in FIGS. 1(a) and 1(b). Referring to FIGS. 1(a) and 1(b), symbols R, G and B respectively denote red, green and blue pixels.
In the configuration shown in FIG. 1(a) , the same color pixels are arranged in the longitudinal (vertical) direction, and red, green and blue pixels are alternately arranged in the horizontal direction. On the contrary, the configuration shown in FIG. 1(b) is arranged in such a manner that red, green and blue pixels are alternately arranged in both of the longitudinal and the horizontal directions.
However, the configuration shown in FIG. 1(a) encounters problems in that the resolution of the displayed lines and pixels is unsatisfactory in the longitudinal direction in which the same color pixels are positioned sequentially, and the apparent color separation capability or the apparent color resolution in the longitudinal direction is unsatisfactory. With the configuration shown in FIG. 1(b), the fact that the same color pixels are arranged sequentially in the diagonal direction downwards to the left causes a problem to arise in that the resolution of the displayed lines and the pixels is unsatisfactory in the aforesaid diagonal direction and the apparent color separation capability or the apparent color resolution is unsatisfactory in the aforesaid direction.
The reason for this will now be described. A large area is occupied by a pixel set which is composed of one red, one green and one blue pixel in the perpendicular direction. In the case shown in FIG. 1(a) constituted in such a manner that one dot is displayed by three pixels arranged in the horizontal direction, that is, one red, one green and one blue pixels, then, for example, two pixels, that is, the green and blue pixels, are invariably present where a red dot is displayed. Therefore, the red dots are displayed at intervals of two pixels, causing a problem to arise in that the realized resolution is unsatisfactory.
In order to compensate for the aforesaid problems, a configuration arranged as shown in FIG. 2 has been suggested. That is, the aforesaid configuration has pixels, the positions of which are deviated from one another from line to line, and the red, green and blue pixels are alternately arranged in the horizontal direction, so that a sequential arrangement of the same color pixels in the longitudinal, horizontal and diagonal directions is inhibited. As a result, the red, green blue pixels are disposed equally, so that the aforesaid problems can be overcome. It should be noted that the horizontal directional deviation between a pixel on the j-th line and that on the j+1 line is made to be 1/2 pixel.
A method of driving an image display apparatus, in which the pixels are arranged as shown in FIG. 2, will now be described.
In the column direction, image data is transmitted as a drive signal from a drive circuit. Referring to FIG. 3, reference numeral 1800 represents an image signal to be used as a TV signal. Referring to FIG. 3, a jH-th (H is the period of the horizontal synchronizing signal) image signal and a (j+1)H-th image signal are positioned adjacently and generally represent substantially the same image data in an ordinary signal.
Referring to FIG. 3, reference numeral 1801 represents a signal expressed by enlarging the signal 1800. Reference numeral 1802 represents a sampling clock signal for sampling image data, the sampling clock signal 1082 having a period which is the same as the time corresponding to one pixel. Thus, sampling is performed at the trailing transitions of the sampling clock.
Therefore, image data A and C are written on pixels a and c on the j-th line and pixels b and d on the j+1-th line, causing the problem to arise in that the resolution of the image substantially deteriorates in the horizontal direction, i.e. the pixels have a deviation from line to line that is not accommodated in the sampled signal.